Along with the rapid development of the display technology, display devices are more demanding than ever before. As an important part of the display device, a backlight source serves as a light source for a display panel. During the manufacture, the backlight source may easily be warped upwardly or downwardly, i.e., the backlight source may be uneven. The display quality of the display device may be adversely affected by the flatness of the backlight source.
Usually, a coordinate measurement machine, a height gauge or a thickness gauge may be used to detect the flatness of the backlight source.
However, the coordinate measurement machine and the height gauge are expensive and cannot be operated conveniently. In addition, they need to be operated by specially trained personnel. For the thickness gauge, sheet-like gauges are inserted into a plurality of gaps between the backlight source and a surface of a working table, and sizes of the gaps are read through the thickness gauge, so as to determine the flatness of the backlight source. The number of the sheet-like gauges needed to be inserted into the gaps may be determined by experience, so a detection result is not accurate, the detection is inefficient, and it is impossible to detect the flatness of the backlight sources on a large scale.